International Dredging Review

International Dredging Review

The Imperial Diversion Dam was built between 1936 and 1938 on the Colorado River approximately 18 miles northeast of Yuma Arizona on River Mile 49.3. The Colorado River in this location forms the boundary between California and Arizona.

The dam built with a storage capacity of 83000 acre-feet at an elevation of 181 was intended to impound river water for irrigation in addition to providing some recreational opportunities for boating camping and fishing. Because of a constant inflow of sediment siltation regularly fills most of the reservoir and builds up at the All American canal and the Gila Gravity main outflow gates. The design was based on periodic dredging behind the dam to maintain reservoir capacity and water deliverability through the gates.

Imperial Dam is approximately 3479 feet long. The dam consists of seven sections that include the California abutment the All American Canal headworks the sluiceway the overflow weir section the Gila Canal headworks the Arizona abutment and the Arizona dike. The Laguna Settling Basin was started in 1963 as a result of a Memorandum of Understanding between Reclamation and the International Boundary and Water Commission dated August of 1961. The agreement was developed to try to reduce the amount of sediment arriving at Morelos Dam.

Work on the basin and associated inlet and outlet channels was completed in 1965. It was designed to require dredging approximately every two years based on an inflow of 350000 to 400000 yards annually and sluicing flows of approximately 5000 to 7500 cubic feet per second. In early 2000 the dredge basin was enlarged by approximately 2000 feet for a total length of approximately 5000 feet extending the time between dredging projects to three to five years depending on the sediment load.

The placement site for all dredged material is at Laguna Basin approximately 16000 feet south of Imperial Dam and adjacent to the Laguna Settling Basin at approximately Colorado River Mile 46.6. Dredged material from previous dredging operations behind the dam and from the Laguna settling basin have been deposited in this 1500-acre area.